Weights and growth rates, feeding ecology, population ecology
and social and spatial organisation of feral goats in the Southern
Uplands of Scotland were investigated between 1977 and 1980. Seven
populations were described as to their origins, breed type and
management.
In general, goats in the eastern populations were significantly
larger than those in the western populations; those in the central
populations were usually intermediate in size. This variation was
probably related to variations in range quality..
Observations and faecal analyses showed that the feeding
ecologies of goats and hill sheep, a potential competitor, were
similar. In general, sheep used freely drained grasslands more
and ate proportionately more grass than goats; the latter, possibly
as a result of competition, ate more ferns, conifers, rica and
rushes than the former. The very heavy use of ferns (bracken) by
goats was discussed in relation to previous studies.
Population size varied between c. 500 and c. 15 depending
partly on the degree of culling. Billies, in general, had lower
survival rates than nannies and together with kids their numbers
varied within populations more than those of nannies. Reasons for
the sex differential in survival and the variability in kid production
were discussed in relation to reproductive behaviour, climate and
population regulation.
Group size varied in a predictable fashion with season, group
type and population size. Complete sexual segregation did not occur
but older billies tended to associate least with nannies, and
especially so in the spring. Goats were spatially organised into
hefts i. e. groups of individuals having highly overlapping home
ranges; in general there was little overlap between heft home ranges
and only billies moved between hefts and then predominantly at the
rut.
The ecology of feral goats was compared with that of other
species with particular reference to the questions of dispersal and
territoriality. Recommendations for improved management and future
research concluded the thesis.